1. Field of the Invention
The present invention relates to a handoff of a mobile communication system, and particularly to an apparatus and a method for accomplishing a soft handoff between mobile communication systems of different generations using a gateway
2. Background of the Related Art
The elements for mobile communication system could be roughly divided into a base station and a mobile station. The base station is divided into a base transceiver station (referred to BTS hereinafter) for performing wireless connection among the mobile stations, a base station controller (referred to BSC hereinafter) for controlling a plurality of the BTSs and performing call mobility management related to a call process.
Also, the mobile communication system could include a mobile switching center (referred to MSC hereinafter) that is responsible for a transmission and reception path for data and control signals to and from another communication network, and a base station manager responsible for operation and maintenance of the whole mobile communication system.
The communication between the mobile station and the base station/controller is performed in accordance with the standard IS-2000, while the communication between the base station/controller and the switching center is performed in accordance with the standard 3G-IOS.
CDMA (Code Division Multiple Access) mobile communication systems have developed on the basis of the standard 2G system such as the standard IS-95 mainly intended for transmission and reception of voice signal, and have been developed in accordance with the standard 3G such as the standard IMT-2000 (International Mobile Telecommunications-2000) where transmission of data in high and ultra high speed as well as voice signal is possible.
However, there is no international standard defined for accomplishing a handoff between the 2G system (referred to low generation system hereinafter) and the 3G system (referred to high generation system hereinafter). Therefore, a method for providing service between the high generation system and the low generation system currently in service, without interruption, is required.
Recently, a soft handoff between the MSCs using a router was realized and provided, which is similar to the soft handoff between the BSCs. In this system, the router performs routing of a signaling message, a traffic message, etc. necessary for the soft handoff between each MSC for the soft handoff to a processor of the system in the target side.
As mentioned above, presently there is no international standard defined for accomplishing a handoff between the low generation system and the high generation system, and the low generation system and the high generation system are different in their backbone, so that a soft handoff between systems of different generations could not be realized using the router currently in use.
In order for the variety of messages necessary for the soft handoff to be transmitted and received between two systems, protocol conversion and paths for a signaling message between the systems and a traffic message should be provided.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.